The present invention relates generally to a suspension system for a hitch mounted to connect a towing vehicle to a trailer.
Most current hitch assemblies merely provide a rigid interconnection between a tow vehicle, such as a pick-up truck, and a trailer, such as a camper or horse trailer, without facilitating adjustment to various load conditions of the trailer during travel over the roads. Such an inability to compensate for driving conditions often results in discomfort for the driver and passenger of the tow vehicle as well as excess wear and tear on both the tow vehicle and the trailer.
Specifically, these hitch assemblies lack an effective means by which to cushion shock created in the fore and aft directions by relative acceleration/deceleration between the tow vehicle and the trailer. These hitch assemblies further lack an effective means by which to cushion shock created in a vertical plane by disparities in pitch angle between the tow vehicle and trailer. Finally, these hitch assemblies lack an effective means by which to accommodate relative rolling motion or tilting that occurs between the tow vehicle and trailer caused by the tow vehicle and trailer being driven or parked on uneven pavement or ground.
Various devices are known in the art for securing a trailer to a pickup truck or similar towing vehicle in a towing configuration. U.S. Pat. No. 2,193,744 to Shriver relates to a fifth wheel hitch in which the trailer-mounted assembly is movable fore and aft against the bias of coil springs that absorb sudden acceleration and deceleration. U.S. Pat. No. 2,093,761 to Kramer relates to a hitch wherein coil springs absorb fore and aft movement of a hitch structure. The hitch structure is mounted on the tow vehicle. These two patents do not contemplate fore and aft cushioning, vertical cushioning or roll accommodation.
U.S. Pat. Nos. 4,861,060 and 4,961,564 to Schult et al. disclose a cushioning air bag in a fifth wheel. The thin air bag 38 is in pneumatic communication with the interior of framing tubes 43 and 44 (best seen in FIG. 6), which interiors serve as the reservoir for the pneumatic air bag. U.S. Pat. No. 5,639,106 to Vitale et al. discloses cushioning air bags in FIGS. 1 and 7. In FIG. 1, four air bags 32 are employed to support the upper structure of the hitch. In the FIG. 7 embodiment of Vitale et al., the two cushioning air bags 57 separate a pivotally connected upper structure, the bags being located between the structure and lower fixed structure at an end of the pivotal structure remote from the pivot. U.S. Pat. No. 5,785,341 to Fenton discloses both a cushioning air bag and a shock absorber disposed intermediate pivotally connected upper and lower structures of the hitch as illustrated in FIGS. 1(a), 2, 3, 4 and 5 of that patent. U.S. Pat. No. 5,328,198 to Adams discloses both a cushioning air bag 15 and a shock absorber 38 located between a pivotal upper portion of the hitch and the lower fixed structure. An elastic band 44 limits the upper movement of the upper pivotal member. U.S. Pat. No. 5,226,675 to Noah et al. discloses an active hitch structure in which sensors detect changes in vertical force to effect pneumatic activation of an air bag 42 as shown in FIG. 3. U.S. Pat. No. 4,580,806 to Kolstad et al. discloses a pivotal upper hitch structure cushioned by an air bag and having a connected shock absorber absorbing vertical acceleration shock of the pivotal upper structure. U.S. Pat. No. 3,208,770 to Freitas et al. discloses a fifth wheel pneumatically cushioned hitch. These patents do not contemplate fore and aft cushioning or roll accommodation.
Accordingly, what is needed in the art is a hitch apparatus that provides fore and aft cushioning, vertical cushioning and roll accommodation as a comprehensive means of improving occupant reducing wear and tear on both the tow vehicle and trailer.
Use of an airbag to cushion a hitch is known. However, without some restraint against hitch supporting structure moving away from the supporting structure under the influence of the air bag, the hitch can be broken during unhitching of a trailer if the airbag is not first deflated. Also, without such restraint, in the event of an accident, a hitch with its supporting structure pivotally connected to the tow vehicle can swing upward and can release the trailer to continue forward to impact the cab of the tow vehicle.
In addition to improved hitch performance and safety, it would be desirable if, upon removal of the uppermost, coupling portion of a hitch, a flat truckbed was left to carry a load.
According to principles of the present invention, a hitch apparatus for removably coupling a trailer to a tow vehicle provides fore and aft cushioning, vertical cushioning and roll accommodation.
In a preferred embodiment, the apparatus comprises a pivotal mount, a carriage slidably secured to the mount and a rockable cradle on the carriage. A mounting assembly for the hitch includes a pair of rails. Each rail is pivotally coupled at a first end with the mounting structure for securing the apparatus to a truck bed or to the trailer. The carriage is mounted on the rails by means of a pair of rail guides, each of which is slidably received on a corresponding one of the rails and is thus slidable in directions fore and aft relative to the tow vehicle and trailer. One or more diagonally extending shock absorbers are pivotally coupled at one end with the truck bed or the trailer on which the apparatus is mounted and pivotally coupled at the other end with the carriage. The cradle is pivotally coupled with and disposed within the carriage so as to be rockable side to side. The hitch is mounted on the cradle.
A first plate (or other member) is mounted on second ends of the rails remote from their pivotal connection to the mounting structure. An air bag is secured to the truck bed directly underneath the first plate when it is the truck on which the apparatus is mounted. A second, fixed plate (or other member) is located on the truck bed directly above the first plate. This second plate limits the upward pivotal movement of the rails and the hitch supported on the rails. In a preferred embodiment, the rails do not pivot upward beyond the horizontal. The limited upward pivotal movement provided by the second plate limits the degree to which the air bag can raise the hitch in the event that one attempts to unhitch a trailer without first deflating the air bag. Also, this limitation on the pivotal upward movement by the rails supporting the hitch prevents the rails and hitch being raised high above the truck bed and coming uncoupled from the trailer in the event of a collision. The tow vehicle occupants are thus protected from the trailer plowing forward into the cab. Of course, when the apparatus is mounted on the towed trailer, the foregoing vertical relationship of parts is reversed; the air bag is located above the first plate between an overhanging trailer part and the pivoted rails and attached plate. It is downward pivotal movement of the rails that is limited by the second plate.
In one preferred embodiment, the hitch supporting provisions are all located below the upper surface of a truck bed. When the hitch is removed from its supporting members, a flat truck bed is left behind to handle a load.